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1.
基于能值分析的农田生态系统服务评估 总被引：2，自引：0，他引：2
农田从供给、调节和支持三个方面为人类提供生态系统服务的同时也消耗着其他系统和人类经济社会对其投入的资源,并且农田还提供了很多无益甚至有害的负服务。本文构建了基于能值分析框架的农田生态系统服务评估体系,以河北省栾城县为代表的农田生态系统为研究对象,从其消耗的资源、生态系统正服务、负服务产出3个方面分析农田生态系统的投入和产出情况;并构建基于生态服务的综合评价指标来探究农田生态系统的可持续发展情况。结果表明：农田消耗了大量的资源（2.75×1020sej）,其中人类的不可更新工业辅助能最大（2.52×1020sej）;农田提供的正服务（6.40×1020sej）主要是供给服务（3.70×1020sej）,负服务供给中（2.02×1020sej）,调节负服务比重最大（1.83×1020sej）;能值可持续发展指数远小于1,且逐渐降低,综合评价农田属于严重的消费型系统。 相似文献
2.
生态系统呼吸在陆地生态系统碳循环中占有重要地位,是碳循环中仅次于生态系统总初级生产力的第二大通量组分。除温度和水分外,生物因子对生态系统呼吸也有着重要的影响。生物因子往往与温度、水分有着相似的季节变化,并且温度还对这些因子有重要的影响,这加深了探讨生物因子对生态系统呼吸影响的难度。复种农田生态系统中生物因子与气象因子季节变化的非同步性为探讨生物因素对生态系统呼吸时间变异的影响提供了有利条件。利用华北平原冬小麦-夏玉米复种农田LAI的季节动态与温度的季节动态存在非同步性这一天然试验条件,本研究通过该农田生态系统连续两年的涡度相关通量观测数据,分析了温度和生物因子对该农田生态系统呼吸季节及年际变化的影响。结果表明,在冬小麦和夏玉米的各个生育阶段,其夜间生态系统呼吸都受到土壤温度的影响,但是这种影响在作物不同的生育阶段有所差异,尤其当土壤温度与叶面积指数（LAI）的季节变化非同步时,LAI会改变土壤温度对生态系统呼吸的控制。基于直线回归方程,LAI能分别解释2003年和2004年冬小麦生态系统参考呼吸（10 ℃下的生态系统呼吸速率）变异的97%和74%,能分别解释夏玉米生态系统参考呼吸变异的85%和42%。华北平原冬小麦-夏玉米复种农田的生态系统呼吸呈“双峰”季节动态模式,且与生态系统总初级生产力及LAI的季节动态模式相一致,两次峰值分别出现在冬小麦的LAI和夏玉米的LAI达到最大时。冬小麦农田生态系统呼吸的最大值在2003年和2004年分别为6.6gC/（m2·d）和5.5gC/（m2·d）,夏玉米农田生态系统呼吸的最大值在2003年和2004年分别为7.7gC/（m2·d）和6.9 gC/（m2·d）。冬小麦农田生态系统在2003年和2004年2个生育期的总呼吸量分别为402gC/m2（累计220天）和486gC/m2（累计232天）。夏玉米农田生态系统在2003年和2004年两个生育期的总呼吸量分别为557gC/m2（累计131天）和481gC/m2（累计107天）。冬小麦及夏玉米生育期生态系统呼吸的年际差异受土壤温度和受LAI影响的生态系统总初级生产力的协同作用控制。冬小麦秸秆还田引起的生态系统呼吸底物的增加以及夏季降雨对土壤湿度的改善都促进了夏玉米生长前期生态系统CO2排放量的增加。相对于自然生态系统,农田生态系统受到更多的管理措施的影响,因此在未来的研究中,应加强农业管理措施以及人类活动对农田生态系统呼吸影响的研究。 相似文献
3.
自然生态环境是城市生态系统赖以生存和发展的重要物质基础，生态足迹作为生态环境承载状态测度的指标，受到社会、经济、人口等多种因素的影响，表现出时空动态性和不确定性特征。鉴于集对分析(SPA)在处理不确定性问题的优势，以武汉市为研究对象，将城市总生态足迹与其相关影响因子联系起来考虑，融合集对分析中的同异反模式识别的“择近原则”和聚类分析思想构造集对分析动态模型，模型精度较高，验证误差均小于0.3%。并对武汉市2005年～2020年总生态足迹发展趋势进行了预测。研究结果表明，2005年～2020年总生态足迹将由1 784.662×104hm2增长到2 781.388×104hm2，呈现出低于GDP、高于能源利用率增长速率的趋势，生态环境将进一步恶化，对此就武汉市生态系统的发展提出了对策与建议。最后，指出SPA动态模型对城市生态系统中生态足迹动态化方法的修正具有理论和实际意义。 相似文献
4.
1986年~2005年三江平原水田与旱地的转化特征 总被引：13，自引：0，他引：13
在遥感和 GIS 技术支持下,通过获取研究区 1986 年、1995 年、2000 年和 2005 年 4 期土地利用数据,从总量态势、相互转化差异、空间格局等三方面分析了3江平原 1986年~2005 年水田与旱地相互转化特征。结果显示： ①三江平原水田和旱地均呈显著增加趋势,水田面积增加的幅度大于旱地,由 1986 年的 57.7×104hm2 增加到 2005 年的 150.9×104hm2,增加面积占三江平原总面积的 13.86%;水田在此期间的动态度为 5.08%,开发速度明显快于旱地;② 水田与旱地的总量变化存在明显的阶段差异,1986年~1995 年,旱地的开发速度是3个时段中最快的,1995 年~ 2000 年是水田面积增长最快的时期,动态度高达 36.49% ;③ 水田与旱地的相互转化特征在不同阶段差异较大,1986年~1995 年为水田转化为旱地最明显的时期,转化面积为 33.1×104hm2;1995年~2000 年为旱地转化为水田幅度最大的时期,转化面积达 63.5×104hm2;④ 水田与旱地相互转化存在明显的区域特征,水田和旱地的重心总体上均表现为向东北偏移的趋势,水田重心的整体偏移量要远大于旱地。 相似文献
5.
基于能值分析的农田生态系统服务评估——以河北省栾城县为例 总被引：1，自引：0，他引：1
农田从供给、调节和支持三个方面为人类提供生态系统服务的同时也消耗着其他系统和人类经济社会对其投入的资源,并且农田还提供了很多无益甚至有害的负服务。本文构建了基于能值分析框架的农田生态系统服务评估体系,以河北省栾城县为代表的农田生态系统为研究对象,从其消耗的资源、生态系统正服务、负服务产出3个方面分析农田生态系统的投入和产出情况;并构建基于生态服务的综合评价指标来探究农田生态系统的可持续发展情况。结果表明:农田消耗了大量的资源(2.75×1020sej),其中人类的不可更新工业辅助能最大(2.52×1020sej);农田提供的正服务(6.40×1020sej)主要是供给服务(3.70×1020sej),负服务供给中(2.02×1020sej),调节负服务比重最大(1.83×1020sej);能值可持续发展指数远小于1,且逐渐降低,综合评价农田属于严重的消费型系统。 相似文献
6.
辽宁省湿地生态系统服务功能价值测评 总被引：21，自引：1，他引：20
货币化评价湿地生态系统服务功能价值,可为湿地资源有效保护与开发决策的制定提供生态经济理论支持。本文依据辽宁省林业厅1995年～2000年对全省湿地资源的调查数据,将辽宁省湿地生态系统划分为近海及海岸湿地、河流湿地、湖泊湿地、沼泽和沼泽化草甸湿地、库塘湿地五大类11种类型,应用生态经济学的理论和研究方法,着重对湿地生态系统提供的物质生产、环境调节和人文社会三大类共8项服务功能的经济价值进行了估算。结果表明：辽宁省湿地生态系统服务功能总价值为741.54×108元/年,相当于全省2000年GDP的15.9%。其中湿地的环境调节功能价值最大,为506.33×108元/年,占湿地总价值的68.3%,物质生产和人文社会服务功能价值分别为185.01×108元/年和50.20×108元/年,其价值比例分别为24.9%和6.8%。辽宁省湿地生态系统服务功能价值主要来源于滩涂、浅海水域、塘库和永久性河流。 相似文献
7.
国家生态压力与生态利用效率研究 总被引：8，自引：0，他引：8
基于生态足迹方法，提出并构建了度量国家生态压力总量与国家生态效率的本国生态足迹和生态利用效率指标。应用该指标对我国1990年～2003年的本国生态足迹、生态承载面积、本国生态赤字及本国生态利用效率进行了计算，分析了中国生态压力、生态利用效率的历史轨迹、发展趋势及其构成和主要矛盾。结果表明，我国的生态系统一直处于超载状态，现在的超载程度已很严重。这一期间我国的本国生态利用效率从2 070元/hm2增长到4 046元/hm2，年均增长率为5.3%。生态利用效率以较高的速度增长，说明我国经济实现了一定程度的生态压力相对减量；但这一时期的生态利用效率的增长率远低于经济总量的增长率，导致本国足迹增长较快。可见，我国经济的快速发展和工业化进程是以本国生态资源的大量消耗为代价的；而能源和农业是中国可持续发展需要解决的主要矛盾。所以，实现可持续发展仅注重环境末端治理是远远不够的，根本途径是从源头实现资源(尤其是能源)需求减量，并应特别重视农业对生态环境的冲击。 相似文献
8.
衡水湖国家级自然保护区湿地景观格局演变分析 总被引：9，自引：1，他引：9
基于1987年、1997年和2005年3期TM遥感数据,对衡水湖的湿地景观空间格局及其演变进行分析,结果表明：该区域以农田为景观基质,水体和芦苇沼泽交错分布构成区域湿地生境的主体斑块,其余景观类型呈以小尺度斑块散布于区域中。保护区湿地景观改变较明显,湿地由1987年的20.2%上升到1997年的23.4%,2005年占到22.3%,农田向湿地类型的转变最为显著,农田和湿地类型之间的动态转换关系很大程度上决定了保护区土地利用结构和景观格局的演变。从景观类型水平来看,表现为水体的平均斑块面积增加,由1987年的3.5187hm2减到1997年的2.0187hm2到2005年为4.3997hm2,破碎度指数下降;聚合度指数和最大斑块指数先降后升,而连接度指数先增后减;芦苇沼泽平均斑块面积下降明显,由1987年的2.6169hm2降到1997年的0.5437hm2,到2005年为0.3558hm2,且形状日趋复杂自然,最大斑块指数和聚合度指数持续减少,而连接度指数的变化趋势则相反,但总体上芦苇沼泽沼泽小面积斑块数量仍占相当比例,破碎化程度仍维持较高水平。在景观整体水平上,保护区的景观多样性和均匀度指数呈缓慢上升趋势,破碎化指数由1987年的51.068增到1997年的74.0985后2005年减为37.88,以农田为景观基质的蔓延度指数则先降后升。景观格局分析表明,衡水湖保护区湿地面积逐步恢复,破碎化程度降低且景观日趋多样化,连通性虽不及1987年历史最高水平却呈加强趋势,湿地生境质量得到优化,2005年湿地恢复的景观格局的空间配置达到3个时期的历史最高水平,也体现了保护区规划管理取得一定成效。 相似文献
9.
基于GIS技术的中国农田磷素养分收支平衡研究 总被引：8，自引：0，他引：8
基于农田养分收支平衡模型、农业经济统计数据,结合GIS技术,从国家、省域、县域3个层面研究了我国农田磷素的平衡特征,并利用GIS技术对研究结果进行了空间表达与分析。主要结论：①我国农田磷素(P)投入总量为610×104t,支出总量为328×104t,农田磷素(P)盈余282×104t,平均单位耕地盈余0.029t/hm2。从大区域来看,我国农田磷素盈余趋势为从我国东部地区农田向西部地区农田逐渐减少;②农田磷素亏缺的县域单元数占全部县域单元数的12.81%,其耕地面积占全国耕地总面积的16.11%。也就是说,虽然在全国层面上磷素赢余量很大,但是并不代表每个县域单元农田磷素都是盈余的,在进行肥料资源宏观配置时必须考虑这些问题;③在全国层面上,磷肥、有机磷肥、其它来源的磷肥占农田磷养分总投入的比例分别为77.11%、22.23%、0.66%,农田磷素养分的投入以磷肥为主,在全国层面上,由人畜禽粪尿提供的磷素占全部有机磷肥投入的比重为85.25%;④全国农田磷素生物产出为294×104t,占农田磷素总支出的比重为89.90%,农田磷素生物产出是农田磷素支出的主要部分。 相似文献
10.
山东省禹城市粮食生产资源利用效率评价 总被引：3，自引：1，他引：3
粮食生产资源利用效率研究是实现粮食稳产、高产的前提，也是保障国家粮食安全的理论基础。对不同条件下的作物生产潜力准确估算和适宜的资源利用效率评价是粮食生产资源利用效率研究的核心内容。本文采用PS123作物生长模型进行作物生产潜力计算，根据山东省禹城市实际状况，确定了模型输入参数，计算了研究区玉米、小麦和大豆的光合、光温、气候和气候－土壤生产潜力，采用作物结构订正计算区域粮食生产潜力。考虑粮食生产中光热资源、水资源、土地资源、社会经济资源等方面，从准则层和因子层两个层面构建了粮食生产资源利用效率评价模型，确定了各评价因子的目标值和权重，对禹城市粮食生产资源利用效率进行评价。研究结果表明： ①山东省禹城市光合生产潜力52 784kg/hm2，光温生产潜力11 023kg/hm2，气候生产潜力8 377kg/hm2，气候-土壤生产潜力6 450kg/hm2，对这3种作物的实际产量进行结构订正得到该市1999年～2001年粮食平均现实生产能力为6 244kg/hm2，禹城市粮食生产潜力较大； ②制约粮食生产稳产、高产主要自然因子为水资源的不合理利用，劳动生产率、化肥利用率和产投比的低下是主要的社会经济限制因子。根据不同的限制性因子，本文提出了单项资源利用技术改进措施。 相似文献
11.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
12.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
13.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
14.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
15.
Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
16.
Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
17.
Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
18.
《中国科学院院刊(英文版)》2014,(3)
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence 相似文献
19.
Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels 总被引：1，自引：0，他引：1
《中国科学院院刊(英文版)》2014,(3):267-268
<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese 相似文献
20.
WANG Sijia 《中国科学院院刊(英文版)》2014,(2):192-194
<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages. 相似文献